Mixtures of fine solid pablk



United States Patent 26 449 PROCESS FOR SEPARATION OF LIQUID FROMLIQUID-SOLID MIXTURES OF FINE SOLID PAR- TICLE SIZE Horace A. Bradt, St.Louis, Mo., assignor to St. Louis Shipbuilding-Federal Barge, Inc., St.Louis, Mo., a corporation of Missouri Original No. 3,053,761, datedSept. 11, 1962, Ser. No.

660,872, May 22, 1957. Application for reissue Aug. 27,

1964, Ser. No. 405,314

8 Claims. (Cl. 210-44) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

This invention relates to improvements in separation of liquid fromsolids and in particular is concerned with the removal of liquid fromcolloidal types of liquid-solid mixtures. This invention finds specialadvantage in the dewatering and drying of phosphate slimes and othercolloidal slimes which have presented various and serious problems inconsolidating the solids and in clarification of the liquid.

In the past, colloidal slurries or slimes containing suspended solids ofvery small particle size have been quite diflicult to dewater properly.A number of methods and applications have been employed with the use offilters, centrifuges, decantation systems and other gravity settlingprocedures. However, due to the finely divided nature of the suspendedsolids which may be in the form of colloidal suspensions, gels, or otherfinely divided and thoroughly dispersed mixtures, resistance to fastseparation of the solids from the liquids has been encountered. Whensuch slimes and slurries are attempted to be separated by filtration,clogging of the filter is a very serious problem. In settling by gravityor decantation, the settling is extremely slow and sometimes completelyineffective.

A particular problem has existed in the handling of phosphate slimeswhich are a principal Dy-product of the pebble phosphate mining process.These slimes have been conventionally consolidated in settling pondsbeyond the limit of compaction by gravity settling alone, if theconditions are favorable for surface evaporation and bottom seepage, butsuch settling of the slime, which is composed of from 95 to 97% water,takes a considerable length of time and requires a large amount of spaceand tie-up of material. Further, the dry produce ultimately obtained isin the form of a hard cake and is required to be broken up for furtherhandling and treatment and is not consistent in make up from top tobottom.

By means of this invention, a process has been devised for the rapiddrying of slimes and slurries comprised of solids of small particle sizeof colloidal nature. As a very signal feature of this invention, theslime to be dried is mixed or agitated to the form of a foam through theuse of foaming agents either as originally contained in the mixture oras added as part of the process. This foam may be suspended over adraining medium for the drainage of water which is subsequently releasedfrom the foam. It might be considered that a form of filtration in thisprocess resembling a non-pressure filter is employed and the foam filmholds the solids in suspension and the liquid runs out by gravity. Theliquid is easily released from the solids while the foam keeps thesolids from clogging the foam supporting member which may be in the formof a filter screen, packed sand, a drainboard, or the like.

In this invention, it might be considered that the foam provides for thedrainage of water by gravity around the discrete bubble particles in thefoam. Thus, although the foam may be whipped into a liquid-solidmixture, so

that the foam formed in solids form a self supporting structure, theexcess water may run down and dram by gravity. In the formation of thefoam, the type of foam i.e., the bubble size, the foaming agent and thevolume of expansion may be varied to suit the type of slurry or slimeemployed.

The foam produced by this invention is in stable form. This is to saythat the foam does not run and is nonfiowin g, and, when placed upon asupport, maintains its form without any substantially slumping orbreakdown. The foam is further prepared from all of the liquid and allof the solids in the solid-liquid suspension, and when foamed the foammaintains its stability while liquid drains from the foam to provide forliquid separation. Further, the foam maintains its stability duringdrying, such as air drying, such that when dried there is solid materialproduced that has a large number of small openings conforming to thebubble size in the foam which the solid material is prepared. Theopenings are in the form of cells so that the material finally preparedfrom the foam is, in the dry form, a collapsible solid mass.

Although the foamed solid liquid mixture has had a substantial amount ofliquid drained from it, the foam film may be further processed inseveral different manners. First of all, the foam film may be exposed tothe atmosphere, in sun light, in an air stream, or to heat for a periodof time for ultimate drying. The ultimate product will be in the form ofa fairly light dry crumbly mass, which may then be crumbled, rather thancrushed to a powder with the particle size remaining relativelyunchanged from that of the original suspended sizes. As anotherembodiment, the substantially dried foam may be collected in paste formbefore it dries completely, or may be extruded to any desired form. Asstill another modification, the foamed particles may be included withpreviously dried discrete material in the form of a fine powder and whencoated, the foamed particles will dry much faster as the dry powderseems to absorb moisture very rapidly. In all modifications, thedewatering and subsequent drying is accomplished in far less time, thanwhen the product is not foamed.

Accordingly, it is the primary object of this invention to obtain asolids separation from a mixture of liquids and finely divided solids bycausing the formation of a foam thereof, either by adding a foamingagent thereto, or by utilizing any foaming properties already containedin the mixture to cause a formation of a foam and separating the liquidtherefrom.

Another object of this invention is to separate liquid from solidmaterial in a slime or slurry of combined liquids and solids which aredifiiculty separable through the use of a foaming process by foaming theslime or slurry and draining the liquid from the foamed material through'a porous base mamber in the form of a screen filter or like manner.

A further object of this invention is to separate liquid fromdiflicultly cfilterable slimes through the use of a foaming process toform a foamed shore and then to drain the liquid from the foamed slimeand dry the remaining particles to a honeycombed solid structure whichis easily crumbled.

Still another object of this invention is to provide a method forseparating liquid from solids in the form of slime by providing afoaming process for the slime to cause it to obtain the form of a foamedslime and to drain the water from the foamed slime and form a resultantpartially dried foamed material in selected particle sizes by pugging,pelleting and the like.

Yet a further object of this invention is to separate solids from aliquid-solid slime mixture by adding a foaming agent or aerating themixture to convert it to a foamed condition to drain the water therefromand cause the coating of discrete particle sizes of the foam with a finedried material in the form of a powder to further the drying of thefoamed particles.

Still another object of this invention is to provide a continuousprocess for separating liquid from a liquidsolid slime mixture byconverting the slime to a foam, through the use of a foaming process andcharging it to the bottom of a tower and draining water from the bottomof the foamed slime through a base member and continually adding freshlyfoamed slime material to the bottom of the tower to cause the drainedfoam to rise within the tower for ultimate removal from the top in acontinuous fashion.

Yet another object of this invention is to dry phosphate slimes by theaddition of a foaming agent to cause the production of foamed phosphateslime and to separate liquid therefrom and to produce an ultimatelydried solid phosphate material in the form of a dried honeycombedstructure.

Further objects of this invention will appear in the detaileddescription which follows and will be further apparent to those skilledin the art.

For the illustration of this invention, particular reference will bemade to the drying of phosphate slimes. The drawing illustratesapparatus for carrying out a continuous process for such drying for thepurpose of example. It is, however, to be understood and as describedabove that this invention is of broader application and may be used forthe foamed drying of slimes in other fields. Thus, any diflicultlyfilterable material in the form of a slime or colloidal or gelatinousstate may be treated according to this invention for the liquid-solidseparation. Thus, the invention may be used for liquid-solid separationin the brewery industry where such liquid-solid mixtures areconventionally encountered. The invention is of broad aspect for theultimate reclamation of either a desired liquid or a desired solid fromthe liquid-solid mixture, depending upon which is the economicallyrecoverable component.

In the mechanics of the liquid separation from the liquid-solid foamedmixture, it is believed that the air bubbles or cells formed by the useof the foaming agent, provide an external film that serves as a mediumfor trapping solids, but at the same time provides a path to carry offthe liquid. Thus, the foam film holds the solids in suspension and theliquid runs out by gravity to the bottom and through a supporting basemember which may be either in the form of a filter screen, packed sandor the liquid may run down slanting run-off boards for removal of theliquid. The important consideration is that the foam suspends the solidsand keeps them from clogging the foam supporting member. For purpose ofconvenience in description the foam supporting member may be describedas a filter screen but is to be understood as to include other drainingmembers.

In the practice of this invention enough foam through the use of afoaming agent, employed either in a prefoamed mix or added directly tothe slime, or by utilizing any foaming properties already in the mix, iswhipped or agitated with the liquid-solid mixture of the slime so thatthe foam film and the solid film form a self-supporting structure afterthe excess water has drained out by gravity. The amount of the foamingagent and the type of foam formed in relation to bubble size andduration of the foam life, can be changed to suit the type of slime andthe consistency of the slime, as will be understood. After the excesswater has drained, the moisture left in the solid and foam film issufficient to make a heavy putty if the material is collected and thismay be pugged before it dries. On the other hand the foamed structurecan be made to retain its shape until it dries. It can then be crumbledinto a powder as its structure is that of a honeycombed easily crumbledmaterial. Both stages of the dewatering of the excess liquid and thesubsequent drying are used for this type of finally dried product andare accomplished in far less time than if the foam had not been formed.In the pugging step only the initial dewatering of the excess liquidfrom the foam is employed.

In order to explain the invention, reference will be made below toparticular applications of the invention with phosphate slimes. It will,however, be understood that other applications may be used. As anexample of other applications besides phosphate slime drying, theseparation of the difiicultly filtera ble trub derived from wort in thebrewing industry may be obtained by practice of this invention. Theprocess may be used in the treatment of coal washing slurries, or theslurries from desliming operations in processing metallic ores or fromindustrial mineral milling, or the slurries that are produced inprocessing non-metallic minerals and powdered rocks production such asare used commercially as pigments, fillers, etc.

The phosphate slimes are quite diflicultly filterable or decantable andthe conventional practice of drying to date has been most cumbersome. Astandard practice of such drying of phosphate slime for the recovery ofthe solid phosphate material requires the usage of large settling pitsin the ground necessitating a great deal of space and a long time ofsettling. The reclaimed solid material finds usefulness in themanufacture of lightweight aggregate or in other cementitious productsfor use in the construction industry, or for use as a fertilizer, rubberconditioner, fillers, as a phosphate charge for electric furnaces, as araw material in the production of phosphoric acid and its byproducts,etc.

In the instant invention, such phosphate slimes which contain to 97%water may be foamed through the use of various types of foaming agents.Conventional foaming agents employed in the concrete industry include:the synthetic detergents such as sodium lauryl sulfate, alkyl arylsulfonate and other types; resin soap and vegetable or animal glue;saponin; alkylated naphthalene sulfonate and degenerated glue, butylatednaphthalene sulfonate and waterglass, and isopropylated naphthalenesulfonate and calcium chloride or high alumina cement; proprietaryneutralized resin; hydrolyzed protein such as keratin (hoof and hornmeal), cattle hooves and fish scales, blood and saponin, and casein. Itwill be readily understood that various difierent types of foamingagents may be employed depending upon the slime used and the form of thedried product desired.

In the use of the foaming agents above-described to provide the foamedslime for the draining of the liquid, it should be pointed out that mereflotation and aeration of the slime does not give the desired rTesults.In flotation and aeration processes air bubbles are formed which carrythe solids to the top. In trying this method of foaming slimes, it hasbeen found that this is unsatisfactory and does not provide for theproper liquid drainage as the foam soon breaks down and does not drainproperly.

For the further explanation of this invention, there are listed below anumber of examples illustrating the separation of liquid from foamedphosphate slimes. The phosphate slimes used are those from the Floridafield in which the percentages of the various components upon adry basisare within the following ranges:

Dry basis percent Loss on ignition (combined water) 9 to 12 Phosphoricacid (P 0 6to 15 Iron oxide (Fe O 2to7 Alumina (A1 0 18 to 29 Lime (CaO)17 to 19 Magnesia (MgO) 0.80 to 1.30 Silica (SiO 30 to 32 Fluorine (F0.20 to 1.00

r Alkalics (Na O) 0.3010 0.40

Example I The phosphate slime comprising 95 to 97% water was mixed witha foaming agent which was prefoamed. This foaming agent was a hydrolizedprotein typified by Mearl type P foaming agent obtained from the MearlManufactoring Corporation of Roselle Park, New Jersey. The agent wasprefoamed by agitation and then added to the slime in a power mixer.Enough foam was introduced to increase the volume of slime to four orfive times the original volume. The mixing was carried out for a halfminute or so until a thorough mixing was obtained. Alternatively thefoaming agent may be added directly to the slime without prefoaming, butit has been found that more foaming agent is required than in the formermethod. Where the foaming agent is added directly, the mixture obtainedis relatively more fluid and may be poured, but still has standupstrength.

After the procedure above outlined, the foamed mixture was placed over afiberglass cloth of 16 mesh. After standing for a short period of time,clear water came through and was recovered, but none of the foamed masscame through. After drainage of one hour, roughly onethird of theoriginal volume of the slime was lost in the form of clear water. Thefoamed slime, after the removal by drainage of most of the liquid, maybe permitted to stand and dry in the atmosphere. Drying in the sun substantially hastens the complete drying and the final dried slime will beof a cellular structure. This material is very easily crumbled which maybe done by taking part of the material and crumbling it between thefingers of the hand as an example of its physical makeup. The finaldrying is not by drainage of liquid through the screen member, but is byevaporation to the atmosphere and the retention of the filmlikestructure accounts for the cellular or honeycomb structure.

By comparison, the same slime dried in a pit without drainage will staywet almost indefinitely. Also, if the slime is attempted to be drainedthrough the screen without the foaming as above described, a substantialpercentage of the slime will actually pass through the screen and willeventually clog it to resist further separation. In present commercialprocedures, water may be decanted from the slime pits, and this watermay be reused in other applications. However, the amount of waterreclaimed will never be as much as that reclaimed in the process of thisinvention. Also, in the decanting operation, if this is carried outdaily on the same slime, the residue will ultimately become fairly thickand after a week or so will be in the form of mud and finally a wet cakewhich dries to hard mass.

The ultimately dried structure obtained through the use of the processof this invention for the phosphate slime, by drying in the atmosphere,provides a product having very small air cells. The material whencrumbled between the fingers is in the form of a light powder which islight enough to blow away. It is to be pointed out that various foamingagents and the type of mixing may be varied to provide larger air cellsand to provide bigger granules, as will be well understood. Likewise,air or inert gases may be forced into the mixer where the foaming agentand the slime are mixed together to modify the cell structure. Also, thefoaming agent may be varied to provide a foam more in the form of apaste with rapid drainage of the water and breaking of the bubblesbefore the slime is dry enough to have a complete cellular structure.This may be desired for other purposes, such as for pelleting or c ssExample II A process similar to Example I was carried out to the pointwhere the foamed phosphate slime was permitted to drain the excessliquid. After this major drainage had been accomplished, the foamyresidue was placed on the top of a tray covered with a bed of previouslycompletely dried slime material in the form of a powder. The tray wastilted, and the slime particles rolled down and coated themselvessomewhat in the nature of breaded oysters. This coating prevented theparticles from sticking to mate rial handling surfaces and provided forready handling. The coated mass of particles of slime was then placed ontwo pieces of asbestos board. One board was dried in the sun at atemperature of F. and 70% humidity and in the space of two and one-halfhours time dried to a material which was readily crumbled. The otherboard was dried indoors out of exposure with the sun and was completelydried in a space of five hours. The foamed material left upon the screenwas dry within a period of two days, showing the advantages of drying bycoating liquid drained slime with previously dried material.

It has further been observed that the dried slimes processed accordingto this invention are of uniform color. This is of substantialadvantage, when compared to the conventional slime drying and crushingof the pit material which is streaked in color indicating separation ofconstituents, and is thereby quite undesirable for some applications. Asfurther advantages over the dried cake from the pit slimes and over andabove the undesirable requirement of crushing the cake in mechanicalcrushers or by bulldozers or the like, the evaporation is greatlyspeeded up by the process of this invention. The particle size of thedried slime product of this invention is quite small and the product isin the form of a powder where desired, as compared to quitesubstantially larger fragments of the crushed caked material from thesettling pits. The dried powder of the product of this inventionpresumably results from the separation of the original slime particles,rather than from a conglomeration as in the pitdried cake material.

Where desired, however, the processed slime of this invention may not becarried to a dried powder form. After the drainage of the liquid fromthe foamed slime, this may be converted in physical form in a pug millor pelleting apparatus, and pellets and briquettes may be formed orextruded like any other plastic material.

In the drying of the partially dried slime, coated with previously driedphosphate material in the form of a powder, it is believed that dryingis hastened by absorption of moisture from within the slime through thedried coating. This is apparently all out of proportion to the amount ofthe coating employed and may be due to the increased surface of exposurecaused by the coated material. This is an observed result aside from anytheoretical discussion to which applicant does not desire to be limited.It has further been found that the coated partially drained foam willdry by evaporation or even by further liquid drainage much faster thanfrom the simple method of Example I, where the foam is merely exposed tothe atmosphere.

Example III As a further example of the rapid drainage of liquid foamedphosphate slime, the following process was carried out. Foamed phosphateslime was placed in a five quart oil can cut out at both the bottom andtop and the can was filled over a bottom screen to a depth of twelveinches. After one hour the enveloping can was removed, and it was foundthat the drainage had been substantially completed and that the foamedslime retained its ex panded mass upon the screen. As a means forcomparison in the same type of apparatus, the can was filled to a depthof two and one-half inches, and it was found that the time for drainageand retention of the foamed mass was about the same. In the drainage ofthe liquid, there may be shrinkage which depends upon the type offoaming agent employed to obtain the foamed slime. Where the foam filmremains long enough for the excess liquid to run off, the foam cellsformed are of substantial duration and less shrinkage will beencountered. Thus, the modification of the physical construction of thefoamed slime to produce the foam obtained by the particular foamingagent is an important consequence of this invention. This modificationof the circumstances is well understood in the art where foaming agentsare quite well predictable upon their known performances.

Example IV The process of this invention may be used to obtain driedslimes in a continuous manner. In the single figure of this invention,an apparatus for carrying out such a process is generally indicated bythe reference numeral 10. This apparatus is in the form of a tank thatmay be as much as sixty feet in height. The tank is provided with afilter screen 11 at the bottom for the drainage of liquid therethrough.The tank has an inlet tube 12 and is connected to a mixer 13 shown inschematic form, to which a foaming agent may be charged together withslime through a line 15. The slime is added to the foaming agent in apre-mixer 16 through a conduit 17, while the foaming agent from the line14 with air or other inert compressed gas from the conduit 18 are addedto the pre-mixer through the conduit 19. In this process, the

foaming agent, which may be either prefoamed or added as the agent, perse, is charged with the slime in conduit 15 to the mixer and mixed to afoamed slime. If desired, air may be added from the line 18 to the mixer13 for additional foaming. The foamed slime is then charged through theconduit 12 to the tower and the tower is filled to the top 20.

As the liquid is separated from the foamed slime by drainage through thescreen 11, further foamed material may continually be added to the tankthrough the conduit 12. This foamed material being of heavier mass thanthe partially dried foamed slime will cause the partially dried foam torise and the material on the top of the tank may then be taken off forrecovery. This continuous process based upon the gravity differential ofthe dried foam with respect to the initial premixed foams saturated withliquid, provides a very convenient method for the first stage drying ofthe foamed slime. After the drainage of liquid, the foamed slime takenfrom the top of the tank may be either further dried to the ultimatehoneycomb form by exposure to the atmosphere, sunlight, or to any typeof evaporation procedure desired, or may be breaded with previouslydried material as described above. Also, the foamed product may bepugged wherein the air is driven off. The foam then disappears and theproduct becomes a putty and is handled thereafter the same as anyplastic material which is extruded or molded.

As will be well understood the foamed slime from the mixer 13 may becharged to the tank through the use of pumps and the like in theexecution of this process. As a further aid in the continuity of thiscontinuous process, it will be observed that there is some shrinkage ofthe par tially dried and liquid drained foam as it rises within thetank. A low hydrostatic head is employed due to the low massive weightof the liquid drained foam which aids in the process.

Example V As a further example of the adaptability of this process, claymay be dried. Florida clay obtained from the bottom of Estero Bay andincluding sand and shell material was screened through a number meshscreen to remove the shells and coarse materials. This clay was washedwith fresh water two to three times and was then decanted in a vessel toremove the muddy water from the sand. The remaining clay slurry willsettle in water in contrast to the phosphate slimes. However, thisinvention finds advantage in the settling and dewatering of the muddywater slurry. Thus, the clay slurry was foamed by the use of a foamingagent in the manner described in Example I and water was drained outmuch faster than where no foaming of the slurry was employed. The sameresults have been observed with Vermont clay which does not contain theshell of the Estero Bay clay but does contain a substantial amount ofsand.

Ill

In these experiments, it has been observed that where cement, sand orsilica flour or other matters are present in the slime or slurry, waterruns out faster from the foam. The nature of the material quitedefinitely affects the rate of water release, and as observed above inExample V the water release from clay slurry is quite rapid as comparedto the phosphate slimes.

Example VI As a further example of the adaptability of this process,expanded mica, commonly known as Zonolite, has been treated according tothe process of this invention to retard moisture absorption. SuchZonolite or vermiculite is commonly mixed with clay to form facing tile,etc., in which moisture absorption is disadvatageous. It has been foundthat these materials, when coated with the foamed slimes of thisinvention and subsequently fired, provide a product that is imperviousto water.

As a contrast to the use of foamed slimes, Zonolite particles were mixedwith an unfoamed slime so that they were fairly well coated and themixture was then dried. This provided a hard undesirably brittlematerial which when broken would break the particles of Zonolite.

When treated by the teaching of this invention, it was found thatZonolite could be mixed with the phosphate slime and foamed through theuse of a foaming agent. The foamed material was then screened and waterwas rapidly drained off to give a dry product of the original sizeparticles with a phosphate coating. This is useful for the production oflightweight concrete, ceramic products etc., as it is quite light andnon-hygroscopic when fired, which is a very advantageous characteristic.

There has been described above a process for very convenientlyseparating liquid from solids in slimy, gelatinous, or colloidalmixtures which are normally quite difficult to separate. In the past,the separation of such very difficultly filterable materials has beenquite a problem in the use of conventional screens, filters, decantersand the like. The teaching of this invention makes possible theseparation of such liquids and solids to provide the desired end productin variable forms. The invention has been described to provide a broadteaching for liquid solid separation. Although it has been found thatparticular suitability exists in the field of drying of phosphate slimesas described above and in the brewing industry, other applications willbe quite readily apparent as indicated in various portions of thisdescription.

Various changes and modifications will be apparent to those skilled inthe art. Such changes and modifications are within the teaching of thisinvention as defined by the claims appended hereto.

What is claimed is:

l. A process for separating dimensionally stable solid discrete matterand liquid matter out of a liquid slurry suspension of the solid matterand wherein said liquid slurry suspension is an aqueous slurrycontaining solid inorganic particles, comprising: adding a foaming agentto the liquid suspension, agitating the mass thus produced until asingle self-supporting stable non-flowing foamy mass of small bubblesize sufficient to maintain the stability of the foam is formed from allof the liquid and the solid matter and in which the foamy mass comprisesa film containing the solid particles in discrete form, placing the foamon a supporting surface and thereafter draining the major portion of theliquid in substantially solid free form from the solids of the foamymass and from said supporting surface to provide a foamy mass containingdiscrete solid particles and passing the drained liquid from saidsurface to a clarified liquid receiving means.

2. A process for drying dimensionally stable solid discrete matter in aliquid-solid mixture containing the solid matter, comprising: adding afoaming agent to the liquidsolid mixture, agitating the mass thusproduced until a single self-supporting stable non-flowing foamy mass ofsmall bubble size sufiicient for stability of the foam until air driedis formed from all of the liquid and the solid matters and in which thefoamy mass comprises a film containing the solid particles in discreteform, thereafter removing liquid by at least partially draining a majorportion of the liquid in substantially solid free form from the foam,and finally drying the foam in stable form to produce a dry, cellular,collapsible frangible solid mass containing solid particles in discreteform.

3. The process of claim 2 wherein the foam comprises a mass of liquidand solids permeated by tiny bubbles, the solids being evenlydistributed therethrough, and wherein there is a step of [the] liquiddraining comprising [comprises] supporting the mass on a filter andcausing the liquid to drain through the filter, the density of the foamsupporting the solids above the filter as the liquid descends throughand away from the foam, so that the solids do not descend upon thefilter in mass to clog the same.

4. The process of claim 2, wherein the foamy mass [from which liquid hasbeen drained and] which is partly wet, is broken into small parts and isintimately mixed with a powder, so that the particles are coated withthe dried powder and air drying the same.

5. A process for separating solid discrete matter and liquid matter outof a liquid slurry suspension of the solid matter and wherein saidliquid slurry suspension is an aqueous slurry containing solid inorganicparticles, comprising: adding a foaming agent to the liquid suspension,agitating the mass thus produced until a single self-supporting stablenonfiowing foamy mass of small bubble size sufficient for stability ofthe foam until air dried is formed from all of the liquid and the solidmatters and in which the foamy mass comprises a film containing thesolid particles in discrete form, placing the foam on a supportingsurface thereafter draining a major portion of the liquid insubstantially solid free form from the foam and from said supportingsurface and passing the drained liquid from said surface to a clarifiedliquid receiving means, and finally drying the foam in a stable form toproduce a dry, cellular, collapsible frangible solid mass containingsolid particles in discrete form.

6. The process of claim 5 wherein the original material is a phosphateslime, and expanded mica is introduced into the initial material andfoamed and dried therewith, to make a dried product consisting of micahaving a phosphate coating.

7. The process of claim 5 wherein the liquid slurry suspension is anaqueous phosphate slime.

8. A dry cellular collapsible frangible solid mass containing solidparticles in discrete form prepared by the process of claim 2.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 737,099 8/ 1903 Hall. 1,064,773 6/ 1912 Richter.1,430,182 9/1922 Peck. 1,439,061 12/ 1922 Broadbridge et al. 1,738,90612/ 1929 Kirschbraun. 1,777,945 10/ 1930 Untiedt. 1,782,383 11/1930Greider 106-122 XR 1,963,030 6/1934 Powell 10640 XR 2,162,379 6/1939Dole et al. 2,562,646 7/ 1951 Sharp et al. 2,725,985 12/1955 Howard etal. 2,729,334 1/1956 Schwarz et al. 2,778,499 l/ 195 7 Chamberlain etal. 2,800,459 7/ 1957 Dijksrnan et al.

FOREIGN PATENTS 741,085 1/ 1953 Great Britain. 118,668 9/1918 GreatBritain.

MICHAEL E. ROGERS, Primary Examiner.

